Consolidate analysis loading helpers

[OrF8]

Summary

• adds shared helpers for explicit daily/weekly value selection
• consolidates directed activity/static-edge CSV loading
• consolidates filtering directed edges to activity-matrix users
• removes repeated inverse-problem window input loading
• preserves all scientific and fallback behavior

Window semantics

• preprocessing, Fano, lagged, and null-model workflows use exact daily match with weekly fallback
• inverse workflows use exact weekly match with daily fallback
• unsupported window values retain their historical fallback behavior
• no window normalization or new validation is introduced

Loading boundary

• shared directed loading preserves activity index conversion and static-edge schema
• shared directed filtering preserves row order, duplicate edges, self-loops, extra columns, and filtered indices
• validation remains in each scientific caller
• inverse-specific loaders remain separate because they normalize different schemas

Compatibility

• existing public signatures are unchanged
• Python 3.9 remains the supported baseline
• notebooks require no edits
• editable-package imports continue to work from external directories

Reproducibility

• lagged synthetic arrays and numerical CSVs match before the refactor
• null-model synthetic numerical CSVs match before the refactor
• all RNG streams and global-state isolation behavior are unchanged
• no real analysis or cached result was regenerated

Validation

• ran the complete unittest suite
• added direct tests for the shared helper module
• characterized all daily, weekly, and unsupported-window dispatch cases
• verified validation order and exception messages
• parsed all source and notebook cells with the Python 3.9 grammar
• compiled source and tests with Python 3.12
• imported all affected modules from an external working directory
• confirmed notebooks, metadata, dependencies, configuration, data, and results are unchanged
• did not run real analysis cells